Mounts of this type are preferably manufactured monolithically. This means that the mount, which is divided into an inner ring and an outer ring, is manufactured by forming slots in a base body, while preserving some material connections between the inner ring and the outer ring. A large number of such mounts known from the prior art differ, in particular, in the design of these remaining material connections, which are substantially defined by the position, geometry and dimensions of the slots and mostly constitute bars or arrangements of bars. Actuators supported in the outer ring, e.g. adjusting screws, act on at least two of said material connections. By initiating an adjustment travel by means of one of said actuators into one of said material connections, the inner ring, and thus the inner ring axis, is moved with respect to the outer ring, and thus the outer ring axis, by a displacement path. The optical element, and thus the optical axis of an optical element mounted in the inner ring, having a fixed position with respect to the inner ring axis allows the position of the optical axis to be adjusted.
The design of the material connections and the direction of an adjustment travel initiated determine the direction of the resulting displacement path and the sensitivity of the translation of the adjustment travel. The design and number of the material connections also determine the rigidity or flexibility, respectively, of the material connections between the inner and outer rings perpendicular to the adjustment plane.
German published patent application DE 199 01 295 A1 discloses an optical assembly with a monolithic mount of the same type, consisting of an outer ring (called outer mount therein) and an inner ring as well as differently designed material connections between the inner ring and the outer ring. The differently designed material connections form solid state hinges or transmissions consisting of solid state hinges.
According to the aforementioned DE 199 01 295 A1, one respective radially acting actuator (in this case, an adjusting screw) acts on each of the material connections in one embodiment of the optical assembly. In the sense of the invention, a respective material connection cooperates with a respective actuator to form a manipulator unit. The adjustment travels respectively initiated by both adjusting screws are sensitively reduced to displacement paths that are independent of each other. In this case, the sensitivity is respectively determined by the transmission of the adjusting screw, the transmission of the lever mechanism and the conversion of the translational movement into a rotary motion about a center of rotation.
This mount is designed for a very small adjustment range, probably from 10-20 μm, and a very sensitive adjustment, probably with a resolution greater than 2 μm, which can be explained by the very low transmission ratio (also referred to as high reduction ratio) of the adjustment travel initiated by the adjustment levers to the resulting displacement paths. The connections are rigid in an axial direction and flexible in a radial direction so as to enable effortless adjustment.
A similar mount with a comparatively larger adjustment range is known from DE 10 2013 109 605 B3. The manipulator units differ from those of the aforementioned DE 199 01 295 A1 in that the material connections forming them are formed by slots with a different geometry. Advantageously, further material connections are present with no adjusting screws acting on them, which, therefore, do not form manipulator units. They merely serve to axially reinforce the mount and can be provided in any number and in any position.
The material connections forming part of the manipulator units are formed by bars having a flexibility distributed over their length. The bars can also be made thicker over their length and thus relatively stiff, if they are tapered at the junctions to the inner ring or the outer ring, respectively, so that these junctions have high flexibility and form flexure hinges. Regardless of their design, the material connections thus formed are soft in a radial direction.
A mount according to DE 10 2013 109 605 B3, mentioned above, is less sensitive than that of DE 199 01 295 A1, also mentioned above, due to a comparatively low reduction of the initiated adjustment travels to displacement paths. In this case, the resolution is 1-2 μm. However, it is suitable for a larger adjustment range of up to approx. 100 μm and can be designed such that it needs to be accessible from one side only for adjustment.
U.S. Pat. No. 7,916,408 B2 discloses an example of a non-monolithic mount, which also consists of an outer ring and a radially adjustable inner ring, arranged coaxially to said outer ring. For adjustment, there are adjusting screws screwed into the outer ring, said adjusting screws enclosing a right angle with each other in a radial direction and each acting indirectly, via a ball, on a pin which indirectly contacts the inner ring via a second ball. Such an arrangement is a manipulator unit in the sense of the invention. Screwing the adjusting screws in causes the inner ring to be displaced in a radial plane. A restoring force opposed to the adjusting screws is caused by a spring-mounted element which contacts the inner ring tangentially. As in the aforementioned monolithic mounts, the manipulator units are soft, i.e. elastic, in the radial plane.
Both the indicated monolithic mounts and the indicated non-monolithic mount are shown by way of example only and could be supplemented by a multiplicity of further mounts of the same type. What they all have in common is that the mount can be moved in a plane perpendicular to the mount axis, which corresponds to the outer ring axis. That is to say, forces acting in this plane may temporarily lead to a basically reversible deflection of the inner ring from its adjustment position. Usually, the positional deviations from the adjustment position of the optical element held in the mount, which result from hysteresis during the return to the adjustment position, are so small as to be within an acceptable tolerance. Where very high precision and stability requirements apply to an optical system, e.g. in the case of high external loads and a required resolution of <1 μm, these positional deviations may, however, be outside said tolerance. Therefore, when very high precision and stability requirements apply, it is of interest to stabilize the adjusted optical element in its adjustment position. In this connection, it is important to ensure, in particular, that no misalignment results from the position stabilization itself.
The aforementioned DE 10 2015 101 384 B3 discloses a mount which comprises an outer ring and an inner ring for holding an optical element, said inner ring being arranged coaxially to the outer ring and being radially adjustable by manipulator units, wherein the inner ring is positionally stabilized, with respect to the outer ring, by the manipulator units in an independent manner via clamping units. The clamping units each comprise two clamping strips, securely connected to the inner ring at one end, two clamping jaws and a pressure screw. As the pressure screw is screwed into the outer ring, the clamping jaws are moved apart, and the clamping strips are clamped against the outer ring, thereby fixing the position of the inner ring and the outer ring relative to each other.
The design of an optical mount according to the aforementioned DE 10 2015 101 384 B3 is justified, in particular, if the fixation of the relative position between the inner ring and the outer ring is intended to be releasable and/or if the mount is exposed to environmental impacts or optical radiation, making adhesives unsuitable for use. This mount has the disadvantage of being very complex both in terms of its mechanism and its manufacture.